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SUMMARY:Superconductivity and magnetism in doped graphene - Andrey Chubuko
 v\, Department of Physics\, University of Wisconsin-Madison\,  USA
DTSTART:20130606T101500Z
DTEND:20130606T111500Z
UID:TALK45716@talks.cam.ac.uk
CONTACT:Helen Verrechia
DESCRIPTION:I discuss possible realization\, in doped graphene monolayer\,
   of a  chiral superconductivity which breaks time-reversal symmetry\,  an
 d exotic  spin-density-wave (SDW) order which preserves full Fermi surface
 .  A unique situation arises in graphene at the critical doping where the 
 Fermi surface is nested and the density of states is singular. In this reg
 ime\, d-wave superconductivity and SDW order   emerge from repulsive elect
 ron-electron interactions. Using a renormalization group method\, I show t
 hat superconductivity wins at the critical doping\, but SDW wins at slight
 ly smaller or slightly larger doping. Superconductivity develops simultane
 ously in two degenerate d-wave pairing channels and   is of chiral type\, 
 with the phase of the superconducting order parameter winding by 4 a
 round the Fermi surface.  Such a state breaks the time reversal symmetry a
 nd exhibit many other fascinating properties.   SDW state is uniaxial\, wi
 th order parameter breaking  O(3) * Z4 symmetry.  I show that this SDW sta
 te is a    half-metal – excitations in one spin branch are gapped\, but 
 excitations in the other spin branch remain gapless and preserve full orig
 inal Fermi surface. Such a state is highly desirable for nano-science as i
 t allows for electrical control of spin currents.
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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